1. Field of the Invention
The present invention relates to an electronic endoscope apparatus, and to an electronic endoscope apparatus that can properly perform correlated double sampling processing according to a temperature of a use environment of a distal end portion of an insertion portion.
2. Description of Related Art
Conventionally, endoscope apparatuses have widely been used for various types of inspections in the medical field and the industrial field. Endoscope apparatuses include an elongated insertion portion, a body portion, and a monitor provided in or connected to the body portion.
In the industrial field, endoscope apparatuses are sometimes used in various temperature environments such as inspections of buildings in outdoor sites with subzero temperatures, inspections of inner portions of jet engines, which have temperatures exceeding 100° C.
A user, which is an inspector, conducts an inspection by inserting an elongated insertion portion into an object to be inspected, and making an image of a site to be inspected, which is picked up by an image pickup device such as a CCD provided at a distal end of the insertion portion, be displayed on a monitor or stored in a storage device.
The image pickup device provided at the distal end of the insertion portion is driven by a drive circuit in the body portion, and an image signal outputted from the image pickup device is subjected to correlated double sampling processing for, e.g., denoising in a correlated double sampling circuit in an image signal processing section in the body portion.
Incidentally, the operation timings of electronic components including semiconductor devices change according to the temperature of the use environment. Thus, for example, Japanese Patent Application Laid-Open Publication No. 2001-54027 proposes a technique that delays the operation timing of a drive circuit for an image pickup device according to the temperature of the digital camera in order to properly process image signals from the image pickup device.